The present invention relates generally to roadway construction method and apparatus, and particularly to a method and apparatus for guardrail assembly and mounting to guardrail posts.
Guardrails are constructed along roadways to prevent unintended exit of automobiles from the roadway. For example, guardrails may be placed along a roadway to prevent an automobile from falling into a ravine or to prevent an automobile from traveling into an opposing flow of traffic. Guardrails are particularly important on curved sections of a roadway where a greater likelihood of inadvertent roadway departure. Indeed, the greater the roadway curvature, the greater the need for guardrails therealong.
FIGS. 1A and 1B illustrate the basic structure of a typical guardrail assembly. In FIG. 1A, a series of guardrail posts 10, one being shown in FIG. 1A, are positioned along a roadway 12. Each guardrail post 10 is partially buried in the earth 14 and includes an upstanding exposed portion 10a. A guardrail support block 16 attaches to the side of post 10, extending toward roadway 12, as a mounting site for a guardrail 18. A post bolt 20 captures the guardrail 18, block 16 and upper portion 10a of post 10 to secure the rail 18 in a given construction and position relative to roadway 12. Thus, each post bolt 20 includes a bolt 20a of enough length to pass through the guardrail 18, support block 16 and guardrail post 10. Typically the bolt 20a includes a square cross-sectional head portion fitting closely within a corresponding square aperture of guardrail 18 whereby the square aperture of guardrail 18 holds bolt 20a against rotation while the nut 20b is tightened with, for example, an impact wrench.
Turning to FIG. 1B, the guardrail 18 comprises a series of rail sections 22, two such sections 22a and 22b being shown in FIG. 1B. Adjacent sections 22 are joined at an overlapping joint 24 by way of splice bolts 26 therethrough. More particularly, splice bolts 26 include a bolt 26a and a nut 26b. The bolt 26a includes a square cross-sectional head portion fitting closely within square cross-sectional apertures of the sections 22 to be joined. In this manner, the splice bolt 26 is tightened by, for example, an impact wrench applied to the nut 26b. Each overlapping joint 24 typically coincides with a post 10, and an additional post 10 typically supports a midpoint of each section 22. Thus, each guardrail section 22 includes at each end a set of bolt apertures for the post bolt 20 and splice bolts 26 to attach the guardrail 18 to a block 16 and post 10 and to form the overlapping joint 24. Also, each section 22 includes a bolt aperture at its midpoint for a post bolt 20 to attach to a block 16 and post 10.
The conventional process of guardrail assembly and mounting typically includes two independent work crews. A post placement crew moves along the roadway placing the posts 10 in the proper spacing, i.e., corresponding to the length of sections 22 to locate posts 10 coincident with each overlapping joint 24 and each midpoint of each section 22. A guardrail assembly crew follows the post placement crew. This second crew must form the overlapping joints 24 and mount the guardrail 18 and blocks 16 to the posts 10. This is traditionally accomplished by manually mounting each section 22 one piece at a time. Thus, the guardrail assembly crew would mount a first section 22 at an end of the guardrail to be constructed, including mounting at its midpoint to a guardrail post 10 and block 16. The unsupported end of this section 22 is then held against a next block 16 and post 10 while a next section 22 is manually located and aligned to bring the two sections 22 together for proper formation of the overlapping joint 24. Once so aligned, the splice bolts 26 and post bolt 20 may be secured to the assembly. The crew continues moving sequentially along the guardrail 18 attaching a single section 22 at a time. Problems typically encountered in this assembly process include difficulty in maintaining alignment of the apertures of the guardrails receiving the bolts 20 and 26, especially on tightly curved roadways.
The post placement crew typically moves much faster than the guardrail assembly crew. A guardrail assembly crew operating according to conventional guardrail assembly practice is a bottleneck in the guardrail construction process. It is estimated that conventional guardrail assembly methods require approximately 0.2 hours per foot of guardrail constructed. It is typical for the post placement crew to work well ahead of the guardrail assembly crew, the guardrail assembly crew always striving to keep the construction project on its time and cost schedule.
It would be desirable, therefore, to improve the guardrail assembly process. In particular, it would be desirable to expedite such process so that a guardrail assembly crew operates at least as fast the post placement crew to reduce the overall time required for guardrail construction. As may be appreciated, the time required to execute a given construction project directly affects overall construction cost. The subject matter of the present invention is directed to improved execution time in the guardrail assembly process, i.e., in the ability of a guardrail assembly crew to mount the support blocks and joined guardrail sections to the guardrail posts previously positioned by a post placement crew.